When air is compressed for use in pneumatic systems and the like, the temperature of the air is raised significantly in the compressor. For example, the outlet air temperature from the compressor may be as high as 350.degree. F. Air at this temperature tends to contain a significant amount of moisture. It is conventional practice to provide some form of moisture removal equipment in the exit stream to remove the excess moisture prior to the use of the compressed air. This is particularly essential when the compressed air is used for machine tool air motors, for painting or for other similar applications where moisture would be detrimental.
Several forms of air dryers are known in the art. Probably the most commonly used equipment for the drying involves some piece of equipment which cools the air and then causes the moisture to condense on a surface such that it can be removed to provide air for the pneumatic systems having substantially reduced moisture content. One such device is described in U.S. Pat. No. 3,359,753, issued to M. Fiedler, et al., on Dec. 26, 1967. In this device the air is caused to pass through a porous material that is maintained at a reduced temperature by the use of a refrigerant passing through coils in this porous material. The condensed moisture is collected and removed through a suitable drain.
Another type of heat exchanger for cooling the outlet air from air compressors is shown and described in U.S. Pat. No. 4,193,443, issued to K. Nanaumi, et al., on Mar. 18, 1980. In this device the moist air first flows past tubes containing air that has been dryed in the device where upon the temperature of the incoming air is moderated. This air then flows through a second portion of the heat exchanger past a plurality of baffles that are connected to tubes carrying a refrigerant. The baffles being at a reduced temperature cause the moisture to condense thereon, and to be deposited in a lower portion of the heat exchanger where they are withdrawn through a suitable drain.
Still another type of heat exchanger for air drying in the compressed air art is that shown in U.S. Pat. No. 4,235,081, issued to R. O. Dowling, on Nov. 25, 1980. This device performs similarly to the heat exchanger of the '443 patent, except that it is physically divided into an air-to-air heat exchanger, and an air-to-refrigerant heat exchanger. The division into these two components reduces some of the cost and complexity of fabrication. Both the device of this patent and that of the '443 patent utilize a plurality of tubes about which the air flow passes to accomplish the heat exchange.
In still other forms of heat exchangers for the cooling of air, it is quite conventional to have duplex tubing wherein air flows through one annulus of the duplex tubing, and refrigerant or predryed air flows in the other annulus. While the duplex form of tubing provides a cooling surface, heat exchangers for a large sized compressor are extensive in size, and thus are difficult to fabricate and to ship, and accordingly are expensive. It is often necessary to utilize tubing bent into a U-shape in order to achieve a given capacity within a specific size limitation.
Accordingly, it is a principal object of the present invention to provide a heat exchanger wherein sufficient cooling surface is provided to dehumidify the air for pneumatic systems, whereby the heat exchanger has a reduced volume for a specific capacity, such that the cost of producing the heat exchanger is substantially reduced.
It is another object of the present invention to use a triple tube array with multiple units in parallel, whereby there is heat exchange accomplished at two surfaces to increase the efficiency of a given size of a heat exchanger.
It is an additional object of the present invention to provide a design for a heat exchanger to be used in the removal of moisture from compressed air systems, which heat exchanger is fabricated using techniques which minimize the cost of the fabrication.
These and other objects of the present invention will become apparent upon a consideration of the drawings referred to hereinafter and the complete description of the invention with regard to those figures.